Download Consultation case: 20 year old female with a left ovarian mass

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Consultation case
20 year old female with a left ovarian mass.
The biopsy material was originally submitted as tissue fragments, the largest of which
measured 100x55x45mm. We received 6 formalin-fixed paraffin embedded tissue blocks with
a diagnosis of ‘ovarian strumal carcinoid’
Histology
Microscopically, we described a regressively changed tumor with variable architectural
patterns (solid alveolar areas, areas of trabecular growth and formation of microfollicles
containing homogenous eosinophilic material). The tumor cells were relatively uniform with
focal nuclear anisomorphism, frequently showing nuclear clearing, grooves and rarely,
pseudoinclusions.
Immunohistochemically, the tumor cells were strongly diffusely TTF-1, thyroglobulin and
HBME-1 positive. CD56 and CK19 were focally weakly positive and synaptophysin and
chromogranin negative. Mitotic activity was low.
Diagnosis
Follicular variant of papillary carcinoma arising in a monodermal ovarian teratoma (struma
ovarii).
Differential diagnosis:
- Metastasis of thyroid carcinoma to the ovary
- Strumal carcinoid
- Sertoli-Leydig tumor
Discussion
Struma ovarii (ovarian teratomas comprising over 50% thyroid tissue) account for less than
5% of all ovarian teratomas. They are usually unilateral and most patients are in their 5th
decade. Malignant transformation is observed in only about 5% of cases. Criteria for
diagnosis of malignancies in struma ovarii are the same as those for diagnosis of malignancy
in the thyroid gland. Papillary carcinomas are diagnosed based on nuclear features (optical
clearing, elongation, overlapping, grooves and pseudoinclusions) while follicular carcinomas
are more diagnostically challenging as struma ovarii lacks capsules and tends to have irregular
margins. Metastatic spread of papillary carcinomas arising in struma ovarii is usually to the
peritoneum, mesenterium and omentum.
HBME-1 positivity is indicative of malignancy but does not imply papillary differentiation.
CK19 is expressed in papillary carcinomas and though it is also focally expressed in reactive
follicular cells it is not seen in follicular proliferations.
It is necessary to distinguish primary malignancy in struma ovarii from thyroid carcinoma
metastatic to the ovary. In cases of metastasis, ovarian involvement is usually bilateral and the
ovaries have no teratomatous features.
The prognosis of thyroid-type malignancy arising in struma ovarii is difficult to estimate due
to its rarity and the lack of a standard approach to treatment.
Reference
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